1. Field of the Invention
The invention relates to a lever-operated hoist, and more particularly to a lever-operated hoist having a structure for continuously pulling down not only the chain at the side being coupled with the lower hook of the load chain, but also the chain at the side not coupled, in a no-load state.
2. Description of the Prior Art
A conventional lever-operated hoist was provided with an operation lever for continuously pulling down the load chain in a no-load state, that is, in a state having no load applied on the lower hook of the load chain.
In such no-load state, when pulling down the lower hook, by operation lever is manipulated to depart the pressure drive member from the friction member so as to be cleared also from other members, and in this state the chain of the lower hook side is moved downward. On the other hand, when pulling down the chain at the side of the end not coupled with the lower hook (at this time, the chain of the lower hook side is pulled up), the operation lever is manipulate to depart the pressure drive member from the operating wheel, and the end side chain is moved downward.
However, as mentioned below, such operation lever structure was not able to pull down the load chain continuously in no-load state, actually, and its improvement has been demanded.
That is, in no-load state, when the lower hook side chain is pulled down and the drive shaft is rotated, the pressure drive member slidably screwed into the drive shaft should ideally rotate together with the drive shaft en bloc, but actually it rotates slightly behind the rotation of the drive shaft due to inertia. In this case, the pressure drive member rotates relatively on the drive shaft to move in the direction of pushing the friction member. Thus, the reverse rotation preventive wheel and the pressure bearing member fixed on the drive shaft are combined into one body to stop rotation of the drive shart in the hoisting-down direction. As a result, rotation of the load sheave coupled with the drive shaft is stopped, and the lower hook cannot be moved downward. Consequently, every time the lower hook stops moving, it is necessary to manipulate the operation lever to depart the pressure drive member from the friction member.
To the contrary, when pulling down the end side chain, the pressure drive member moves in the direction of contacting with the operating wheel reversely to the case above, and contacts flatly with the end surface of the operating wheel. In this case, since the rotating action of the operating wheel is somewhat receiving a resistance in relation with the operation lever, the rotation of the drive shaft itself receives also resistance through the pressure drive member. Accordingly, the end side chain can be hardly pulled downward, and it is every time necessary to repeat the operation of manipulating the operation lever to pull the pressure drive member from the operating wheel.